J. Clément

Influence of breathing therapy on complaints, anxiety and breathing pattern in patients with hyperventilation syndrome and anxiety disorders

The effect of breathing therapy was evaluated in patients with hyperventilation syndrome (HVS). The diagnosis of HVS was based on the presence of several suggestive complaints occurring in the context of stress, and reproduced by voluntary hyperventilation. Organic diseases as a cause of the symptoms were excluded. Most of these patients met the criteria for an anxiety disorder. The therapy was conducted in the following sequence: (1) brief, voluntary hyperventilation to reproduce the complaints in daily life: (2) reattribution of the cause of the symptoms to hyperventilation: (3) explaining the rationale of therapy-reduction of hyperventilation by acquiring an abdominal breathing pattern, with slowing down of expiration: and (4) breathing retraining for 2 to 3 months by a physiotherapist. After breathing therapy, the sum scores of the Nijmegen Questionnaire were markedly reduced. Improvements were registered in 10 of the 16 complaints of the questionnaire. The level of anxiety evaluated by means of the State-Trait Anxiety Inventory (STAI) decreased slightly. The breathing pattern was modified significantly after breathing retraining. Mean values of inspiration and expiration time and tidal volume increased, but end-tidal CO2 concentration (FETCO2) was not significantly modified except in the group of younger women (< or = 28 years). A canonical correlation analysis relating the changes of the various complaints to the modifications of breathing variables showed that the improvement of the complaints was correlated mainly with the slowing down of breathing frequency. The favorable influence of breathing retraining on complaints thus appeared to be a consequence of its influence primarily on breathing frequency, rather than on FETCO2.

Total respiratory impedance measured by means of the forced oscillation technique in subjects with and without respiratory complaints

The purpose of this study was to determine whether the forced oscillation technique is more sensitive than spirometry to detect lung function alterations in subjects with respiratory complaints. The input impedance of the respiratory system (between 2 and 24 Hz) and maximal expiratory flows and volumes were measured in 1,255 subjects referred for routine spirometry. A questionnaire concerning respiratory complaints was administered. A discriminant analysis was performed between subgroups of subjects without (137 males and 140 females), with moderate (115 males and 109 females) and with marked respiratory complaints (149 males and 132 females). A clear-cut separation was achieved by this analysis only between those subjects without and with marked complaints. Both lung volumes and flows as well as impedance parameters (mean value and frequency dependence of resistance in females, mean resistance in males) contributed to the discrimination of subjects without and with marked respiratory complaints, although there was only a moderate decrease of discriminative power when the impedance parameters were excluded. The contribution of the forced oscillation parameters to discriminative power was larger in females than in males (40 vs 19%), which may be related to the higher prevalence of asthma in our population of females. Excluding the subjects with marked functional impairment improved the share of forced oscillation parameters only slightly with respect to lung volumes and flows (females 54 vs males 23%). Considered separately, however, the sensitivity of spirometry and forced oscillation technique to detect symptomatic people appeared to be similar. We conclude that impedance measurements by forced oscillation technique and routine spirometry are both associated with respiratory complaints. Our results indicate that the information provided by impedance measurements can be complimentary to that obtained by spirometric indices.

Unsteadiness of breathing in patients with hyperventilation syndrome and anxiety disorders

The breathing pattern of 399 patients with hyperventilation syndrome (HVS) and/or with anxiety disorders and that of 347 normal controls was investigated during a 5 min period of quiet breathing and after a 3 min period of voluntary hyperventilation. The diagnosis of HVS was based on the presence of several suggestive complaints occurring in the context of stress, and reproduced by voluntary hyperventilation. Organic diseases as a cause of the symptoms were excluded. The anxiety disorders were diagnosed by means of an abbreviated version of the Anxiety Disorders Interview Schedule (ADIS). There was a large overlap between the two diagnoses. Simply breathing via a mouthpiece and pneumotachograph made end-tidal CO2 fractional concentration (FET,CO2) decrease progressively both in hyperventilators and in patients with anxiety disorders, but not in normals. At the start of the measurement the FET,CO2 was not different between patients and healthy subjects. In patients < or = 28 yrs, the decrease of FET,CO2 resulted from a higher tidal volume, and in patients > or = 29 years from an increase in frequency. After voluntary hyperventilation, the recovery of FET,CO2, was delayed in patients, due to a slower normalization of respiratory frequency in females and in older males, and of tidal volume in younger males, and also due to less frequent end-expiratory pauses. When breathing was recorded first by means of inductive plethysmography (Respitrace), the progressive decline of FET,CO2 seen in patients was not observed: from the onset of the recording, FET,CO2 was reduced in patients. It did not change further when, immediately afterwards, the subject switched to mouthpiece breathing. The finding that breathing through a mouthpiece induces hyperventilation in patients and that recovery of FET,CO2 is delayed after voluntary hyperventilation, suggests that the respiratory control system is less resistant to challenges (mouthpiece or voluntary hyperventilation) in those patients. On the other hand, the lower values of FET,CO2 measured during recording by means of a Respitrace probably result from a challenge, prior to the recordings, induced by the fitting of the measuring device to the patient. This unsteadiness of breathing characterizes patients with hyperventilation syndrome and those with anxiety disorders, but is not sufficiently sensitive to be used for individual diagnosis.

Short-term ventilatory effects in workers exposed to fumes containing zinc oxide: comparison of forced oscillation technique with spirometry.

Following the occurrence of metal fume fever in some subjects after the installation of an electric furnace in a steel plant, a survey was undertaken to examine whether subjects exposed to fumes containing zinc oxide would exhibit a detectable impairment in ventilatory function, and whether a forced oscillation technique (FOT) was more suited for this detection than conventional spirometry. Pulmonary function measurements were made in 57 exposed workers (production or maintenance) and 55 nonexposed workers (maintenance or strandcasting department) at the beginning and near the end of a work shift (day or night). Maximal expiratory volumes and flows were measured by means of a pneumotachograph, and respiratory resistance (Rrs) and reactance at various frequencies by means of a FOT. These measurements were repeated 1 day later. During the day shift, there were no significant differences in pulmonary function between exposed and control workers. However, during the night shift, an influence of exposure on pulmonary function was revealed both by spirometry and by FOT: workers exposed at night showed a slight decrease in vital capacity (VC) and in forced expiratory volume in one second (FEV1), and a decline in respiratory resistance (Rrs) with oscillation frequency, that were more marked than in unexposed subjects. In contrast to the frequency dependence of Rrs, the changes of lung volumes and expiratory flows were related to differences in initial values between exposed and nonexposed workers. The decrease in FEV1 was maintained the day after exposure. The forced oscillation technique proved at least as sensitive as spirometry to detect small across-shift changes in ventilatory function. Although the effects on pulmonary function were small, it is likely that they represent a subclinical response to the inhalation of small quantities of zinc oxide.

Course and prognosis of patients with advanced chronic obstructive pulmonary disease. Evaluation by means of functional indices.

Abstract A homogeneous group of 64 patients with advanced chronic obstructive pulmonary disease (COPD) and hypercapnia was followed from 2 to 15 years. Three quarters of the patients died during the period of study. Fourteen functional parameters were repeatedly measured under stable clinical conditions. Their importance for prognosis was assessed by means of a discriminant analysis performed on the initial values and the evolution with time of the parameters. The initial values, closely related to a bad prognosis (average survival of 6 years), are arterial carbon dioxide tension and oxygen saturation during exercise, especially variation of the latter caused by exercise, and the diffusing capacity for carbon monoxide. Once chronic hypercapnia has been reached, evolution of the disease is characterized, first, by a period of stability of all functional parameters, but with an evolution of the electrocardiogram towards cor pulmonale. This period is followed, on the average 8.5 years before death, by a rapid deterioration of one second forced expiratory volume, vital capacity, arterial carbon dioxide tension, oxygen saturation during exercise and diffusing capacity. Finally, during the last years of life, the functional condition of the patients is dominated by a marked decrease in oxygen saturation at rest.

Errors in the measurement of total respiratory resistance and reactance by forced oscillations

The total respiratory resistance determined by means of the forced oscillation technique during spontaneous breathing demonstrates a variability which may be due (1) to variations of the resistance itself, (2) to the superposition of rapid oscillatory and slow respiratory signals, (3) to the presence in the breathing signals of harmonics the frequency of which is the same as that of the oscillations. In the present study we investigate the importance of the third cause of variability, in a mechanical system in which causes 1 and 2 have been excluded. It is shown that the presence of high frequency components in breathing is an important source of error in the measurement of instantaneous resistance and reactance. The error is larger at higher frequency and amplitude of breathing, lower frequency and amplitude of forced oscillations, and in the presence of a high respiratory impedance. The error is likely to be negligible when the frequency of the forced oscillation is high (e.g. 30 Hz). At lower frequencies, theinfluence of harmonies in breathing can be corrected by calculating average resistance or reactance values over one or more respiratory cycles.

Expiratory flow rates, driving pressures and time-dependent factors. Simulation by means of a model

Abstract Flow-volume and isovolume pressure-flow relationships were simulated using a hybrid computer. The model, which represents a single homogeneous bronchus, shows that there is no unique relationship between flow and driving pressures: flow rates depend not only on simultaneous driving pressures but on the previous rate of change of pleural pressure. This dependence, which is responsible for the scatter of the points on the isovolume pressure-flow graphs, is due mainly to the viscous airway wall resistance. According to the model, the latter resistance is more effective in delaying airway collapse than airway wall inertia or airway flow. Wall resistance alone, however, cannot prevent complete airway collapse.

Influence of the mediastinum on the measurement of esophageal pressure and lung compliance in man.

SummaryThe influence of mediastinal organs on esophageal pressure was estimated in man from the variations of esophageal elastance and amplitude of the cardiac oscillations. From the simultaneous measurements of both parameters and of esophageal pressure at different lung volumes and levels in the esophagus, in the sitting and supine positions, using a 3 and 10 cm long ballon, at rest and during exercise, it was concluded: 1. The difference in measured pulmonary compliance with posture is mainly due to a mediastinal artifact, acting primarily at high lung volumes in the sitting position. In the supine position mediastinal loading is more pronounced but does not vary with lung volume (between 10 and 90% of vital capacity). 2. The vertical esophageal pressure gradient is more pronounced in the lower half of the esophagus. It is probably estimated correctly at that level but underestimated at higher levels. Pressure irregularities observed along the esophagus in the supine position are due to local actions of mediastinal organs. 3. The difference in pressure obtained with balloons of different size can be attributed to the influence of the elastic properties of the esophageal wall, provided one takes into account the vertical pressure gradient, and to shifts in the site of pressure recording in the longer balloon. 4. The increase in pressure without change of pulmonary compliance observed during exercise is also a mediastinal artifact. 5. Extrapolation of esophageal pressure towards zero balloon volume successfully corrects for the influence of posture on pulmonary compliance. However, this procedure does not allow for an estimation of intrathoracic pressure in the presence of a marked mediastinal compression effect.

Influence of flow amplitude on pulmonary resistance determined near zero flow

Pulmonary resistance, determined near zero flow by means of the isovolume technique, increases with the total amplitude of flow. This variation observed in healthy subjects at two frequencies, and documented also by other investigators, was stimulated in a model study. The main factor responsible for the amplitude dependence of pulmonary or airway resistance appears to be the asymmetrical elastic characteristics of the airways.

Respiratory Failure: Correlation between Encephalopathy, Blood Gases and Blood Ammonia

In 59 patients with respiratory insufficiency due to chronic obstructive pulmonary disease (COPD) the relationship between the state of consciousness, the blood gases and blood ammonia were studied. Interindividually, a significant correlation was found between the encephalopathy and SaO2, PaCO2 or ammonia, and also between the blood gases and ammonia. On the other hand, an intraindividual study, performed on patients with minor cerebral dysfunction, showed that only PaCO2 was significantly correlated with the stage of consciousness. Ammonia did not appear to have a neurotoxic influence. The ammonia level seemed to be influenced primarily by other factors than the blood gases, although there was a borderline influence of SaO2 on aterial ammonia and a significant influence of PaCO2-HCO3 and pH on venous ammonia.